Person: Ortega Menor, Lorena
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First Name
Lorena
Last Name
Ortega Menor
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Geológicas
Department
MineralogÃa y PetrologÃa
Area
CristalografÃa y MineralogÃa
Identifiers
30 results
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Item The Patricia Zn–Pb–Ag epithermal ore deposit: An uncommon type of mineralization in northeastern Chile(Ore Geology Reviews, 2016) Chinchilla Benavides, DarÃo; Ortega Menor, Lorena; Piña GarcÃa, Rubén; Merinero Palomares, Raúl; Moncada, Daniel; Bodnar, Robert J.; Quesada Ochoa, Cecilio; Valverde, Antonio; Lunar Hernández, RosarioThe Patricia ore deposit represents an unusual example of economic Zn–Pb–Ag mineralization at the northernmost end of the Late Eocene–Oligocene metallogenic belt in Chile. It is hosted by volcano-sedimentary units, which are typically tuffaceous and andesitic breccias. The ore body consists of a set of subvertical E-W vein systems developed under a sinistral strike-slip regime that included transtensive domains with generalized extensional structures where the ores were deposited. The deposit is divided into two blocks by a set of NNW-ESE-trending reverse faults, which uplifted the eastern block and exhumed thicker and deeper parts of the deposit. At least 200 m of volcano-sedimentary pile hosting the mineralization has been eroded in this block. By contrast, the western block exposes a shallower part of the system where cherts, amorphous silica and jasperoids occur. Three main stages of mineralization have been defined: (1) pre-ore stage is characterized by early quartz, pyrite and arsenopyrite, (2) base-metal and silver stage; characterized by sphalerite (6 to 15 mol% FeS), galena, chalcopyrite, pyrrhotite and Ag-bearing minerals (freibergite, polybasite, stephanite, pyrargyrite, freieslebenite and acanthite) and (3) post-ore stage; characterized by late quartz, kutnohorite and minor sulfides (arsenopyrite, sphalerite, pyrite, galena, Ag-bearing minerals and Pb-sulfosalts). Whole-ore geochemistry shows two groups of elements that are positively correlated; 1) Ag–Cd–Cu–Pb–Zn related to the base metal sulfides and 2) Au–As–Ge–Sb–W related to arsenopyrite and pyrite. Hydrothermal alteration is pervasive in the outcropping mineralized areas, including silicification and locally, vuggy silica textures. At depth, chloritic and sericitic alteration is developed along vein selvages and is superimposed to the regional propylitic alteration. Fluid inclusions indicate that the base-metal ores were deposited from 250 to 150 °C moderate salinity fluids (1–9 wt.% NaCl). The pre-ore stage is characterized by a saline fluid (6–22 wt.% NaCl) and between 210 and 250 °C whereas the post-ore stage has salinity of 4–8 wt.% and temperature from 175 to 215 °C. Cooling was the mechanism of ore mineral precipitation in the Patricia deposit, although mixing of fluids could have occurred in the pre-ore stage. Mineralogical, geochemical and fluid inclusion evidence is consistent with an intermediate sulfidation (IS) epithermal deposit type. This study highlights the high potential for hidden economic mineralization at depth in the western block and for extension of the ore body both to the south and to deeper levels in the eastern block of the Patricia ore deposit. To a larger extent, the implications of finding such polymetallic epithermal style of mineralization in the northern Chile Precordillera is relevant both to the regional metallogenic perspective and to the exploration potential of the region, where the late Eocene–early Oligocene metallogenic belt apparently disappears.Item The role of crustal contamination in the genesis of Ni-Cu sulfide ores from the Cortegana Igneous Complex (SW Spain)(Let's Talk Ore Deposits: Proceedings of the Eleventh Biennial SGA Meeting, Antofagasta, Chile, 26-29 September 2011, 2011) Piña GarcÃa, Rubén; Gervilla, Fernando; Ortega Menor, Lorena; Lunar Hernández, MarÃa Del RosarioCrustal contamination of mafic magmas with S-rich country rocks is believed to play a critical role in the formation of Ni-Cu sulfide ores in SW Spain. Whereas this process has been well recognized in the Aguablanca Ni-Cu deposit (the only economic ore of this type in SW Europe), no data existed in other less mineralized, mafic-ultramafic intrusions of the region, such as the Tejadillas prospect in the Cortegana Igneous Complex. The Tejadillas prospect is composed of igneous cumulates similar to those of Aguablanca, but their incompatible trace element abundances show more primitive patterns than those of Aguablanca. In contrast, incompatible trace element ratios of the Aguablanca rocks are much closer to the contaminant country rocks than those of Tejadillas. Therefore, we suggest that the small volume of sulfide mineralization observed at Tejadillas was the consequence of low degrees of contamination of its parental magma by S-rich country rocks. This suggest that assimilation of S-rich country rocks by mafic magmas is the key factor for the genesis of economic Ni-Cu sulfide ores in SW Spain.Item Distribution of platinum-group and chalcophile elements in the Aguablanca Ni–Cu sulfide deposit (SW Spain): Evidence from a LA-ICP-MS study(Chemical geology, 2012) Piña GarcÃa, Rubén; Gervilla, Fernando; Barnes, Sarah-Jane; Ortega Menor, Lorena; Lunar Hernández, RosarioThe concentrations of platinum-group elements (PGE) and chalcophile elements Ni, Co, Au, Ag, Se, Re, Cd, Bi, Te and As have been determined by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICPMS) in base metal sulfide minerals (BMS) from the Aguablanca Ni–Cu deposit, SW Spain. The main aim was to constrain the role played by the BMS as hosts of PGE as this reveals important information regarding the processes controlling the distribution of these elements in the deposit. The BMS (pyrrhotite, pentlandite, chalcopyrite and minor pyrite) occur as semi-massive, disseminated and minor chalcopyrite-veined ores. On the basis of whole rock metal abundances and BMS mineralogy, these ore types have been interpreted to be the result of the fractionation and crystallization of an immiscible sulfide liquid. Platinum-group and chalcophile element concentrations vary as a function of the BMS and ore types. The partitioning behavior of some of these metals during the fractional crystallization of the sulfide liquid largely governed their distribution in the ore. Rhenium, Os, Ir, Ru, and Rh occur mostly in solid solution in pyrrhotite and pentlandite from the semi-massive ore which has been interpreted to represent monosulfide solid solution (mss) cumulates. The mss crystallization gave rise to minor Cu-rich sulfide liquid in the form of chalcopyrite veinlets with relatively Pd-, Au- and Ag-enriched chalcopyrite, and minor Re-, IPGE- and Rhdepleted pyrrhotite and pentlandite. Platinum-group element contents in the BMS from the disseminated ore, interpreted to represent an original unfractionated sulfide melt, are approximately intermediate to the semimassive and chalcopyrite-veined ores. Palladium and Pt occur mostly associated with Bi, Te, and As forming platinum-group minerals (PGM, Pd–Pt bismuthotellurides and Pt arsenides) within individual BMS grains. This preferential location along with the textures adopted (usually rounded grains and laths) and the temperatures of crystallization (inferred below 500 °C) suggests that Pd and Pt, initially dissolved in the BMS, were exsolved along with Bi, Te and As to form the PGM assemblage present in the ore. Some Pd (approximately 30% of the bulk) remains in solid solution in pentlandite for the three ore types. The presence of Pd in pentlandite is likely a combined effect of limited sulfide fractionation with some of Pd remaining in mss and Pd diffusion into pentlandite from the mss and Curich portions on cooling. Two textural types of pyrite hosting distinct PGE concentrations have been described: (1) large idiomorphic pyrite and (2) ribbon-like pyrite. Idiomorphic pyrite is the unique BMS hosting Pt (with contents as high as 15 ppm) and also contains relatively high Rh concentrations (4–31 ppm). By contrast, ribbon-like pyrite has no Pt and hosts similar Os, Ir, Ru and Rh concentrations (30–360 ppb) to those of the host pyrrhotite to that it replaces. The origin of the idiomorphic grains, whether exsolution products from mss or alteration products of pyrrhotite, is not well known and further work will be necessary to constrain this point. Nevertheless, the presence of PGE hosted by pyrite reveals that this sulfide should not be overlooked as a potential carrier of PGE in Ni–Cu–(PGE) ore deposits.Item Estudio petrológico y mineralógico de la mineralización de Cu-(Ag) de tipo manto del prospecto Shaft 40 (Proyecto Minero Picachos, Chile)(Macla, 2018) Baza, Andrea; Piña GarcÃa, Rubén; Ortega Menor, Lorena; Lunar Hernández, RosarioEl Proyecto Minero de Picachos (IV Región, Coquimbo, Chile) es una mineralización de Cu-(Ag) de tipo manto localizada en la Franja Cretácica de los Andes Centrales, y constituye un proyecto de exploración minera desarrollado por la empresa Herencia Resources. Cubre una superficie de unas 410 Ha y hasta la fecha se han definido 5 prospectos de Cu-(Ag), donde la mineralización de sulfuros y sulfosales tiene un claro control litológico y estructural, y aparece como cuerpos diseminados y vetas (Fig. 1a). Actualmente, en la zona se están llevando a cabo trabajos de explotación minera a pequeña escala, con una producción mensual que oscila entre 4000 y 10000 toneladas.Item Estudio Mineralógico del Depósito de Zn-Pb- Ag de Patricia (Paguanta, NE de Chile)(Macla, 2012) Chinchilla-Benavides, DarÃo; Piña GarcÃa, Rubén; Merinero, Raul; Ortega Menor, Lorena; Quesada, Cecilio; Valverde, Antonio; Lunar Hernández, RosarioItem Partition Coefficients of Platinum Group and Chalcophile Elements Between Arsenide and Sulfide Phases as Determined in the Beni Bousera Cr-Ni Mineralization (North Morocco)(Economic geology and the bulletin of the Society of Economic Geologists, 2013) Piña GarcÃa, Rubén; Gervilla, Fernando; Barnes, Sarah-Jane; Ortega Menor, Lorena; Lunar Hernández, RosarioThe partition coefficients of platinum group elements (PGE) and chalcophile elements Au, Re, Ag, Se, Bi, Te, and Sb, between arsenide and sulfide phases (DAs/sulf) have been estimated by measuring in situ concentrations of these elements using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) in coexisting arsenide and sulfide minerals from the Beni Bousera Cr-Ni mineralization (North Morocco). Previous experimental studies and observations on the distribution of PGE in a number of As-rich, Ni-Cu-PGE ore deposits have shown that arsenide minerals may play an important role controlling the distribution of these metals in magmatic sulfide systems. However to date, there is no comprehensive study quantifying the partitioning behavior of these elements when arsenide minerals crystallize either directly from a sulfide melt or from an arsenide melt previously segregated by immiscibility from a sulfide melt. The Beni Bousera mineralization represents an excellent natural laboratory to evaluate these partition coefficients because maucherite (Ni11As8) coexists in equilibrium with pyrrhotite, pentlandite, and chalcopyrite in form of globules mostly associated with pyrrhotite, and arsenide and sulfide minerals account for the bulk of the PGE (with the exception of Pt) and chalcophile elements in the samples. The laser ablation analyses reveal that maucherite is strongly enriched in all chalcophile elements, except Se, relative to sulfide minerals. The calculated DPGEAs/sulf are the following: DIrAs/sulf = 920 DRhAs/sulf = 620, DPtAs/sulf = 330, DPdAs/sulf = 250, DOsAs/sulf = 140, and DRuAs/sulf = 50. For the rest of elements, the obtained values are the following: DSbAs/sulf = 890, DTeAs/sulf = 190, DBiAs/sulf = 50, DReAs/sulf = 6, DAuAs/sulf = 310, DAgAs/sulf = 4, and DSeAs/sulf = 0.6. These results clearly highlight the strong affinity of PGE for arsenide phases and the importance of these phases as potential carriers of PGE in Ni-Cu-PGE ore deposits.Item Zoned chromite records multiple metamorphic episodes in the Calzadilla de los Barros ultramafic bodies (SW Iberian peninsula)(European Journal of Mineralogy, 2014) Merinero Palomares, Raúl; Lunar Hernández, Rosario; Ortega Menor, Lorena; Piña GarcÃa, Rubén; Monterrubio Pérez, SerafÃn; Gervilla, FernandoPodiform chromitites occurring in the ultramafic bodies of Calzadilla de los Barros, in the Ossa-Morena zone of the Iberian Massif (SW Iberian Peninsula), were deformed and metamorphosed together with their host rocks, leading to the development of variably complex patterns of zoning in chromite grains. These patterns consist of cores with variable composition surrounded by thin rims of porous chromite. Two types of zoned chromite are observed in chromitites: (1) crystals with zoned cores characterised by progressive Mg# [¼Mg/(Mg þ Fe2þ)] decrease from inner to outer core, surrounded by Fe2O3-poor, porous rims, and (2) crystals showing the opposite chemical trend in cores (progressive Mg# increase from inner to outer core) and Fe2O3-rich porous rims. Mgrich chlorite is the only silicate mineral forming the matrix of all chromitites and filling most pores in chromite rims. Accessory chromites in dunites show complete transformation to ferrian chromite and Cr-rich magnetite. However, some of them exhibit complex chemical and textural zoning with three concentric zones (from inner to outer core and to inner rim) characterised by progressive Mg# increase and Cr# [¼Cr/(Cr þ Al)] decrease, surrounded by an outer rim with almost the same composition as the inner core. Some chromite grains from massive chromitites (defined here as higher than 85 vol.% chromite) still preserve inner core compositions unaffected by metamorphic transformation. These inner cores show high-Al composition (Cr# ¼ 0.48–0.52) with Mg# ranging from 0.65 to 0.70. These compositions resemble those reported for Al-rich, podiform chromitites in ophiolites elsewhere and indicate that chromitites from Calzadilla de los Barros derived from a MORB melt type in a MORB or supra-subduction zone setting. The chemical and textural variations in zoned chromite from chromitites and dunites can be interpreted in terms of a multistage process characterised by two episodes of retrograde metamorphism separated by a high-temperature heating event. This interpretation suggests a correlation with the tectono-metamorphic evolution of the Neoproterozoic basement of the Ossa-Morena zone.Item New observations by X-ray fluorescence microscopy provide insights for the origin of Aguablanca sulfide-matrix breccias in SW Spain(Macla, 2019) Barnes, Stephen J.; Piña GarcÃa, Rubén; Le Vaillant, Margaux; Ortega Menor, Lorena; Lunar Hernández, RosarioItem Enriquecimiento Hidrotermal en Pd y Pt en Cromititas Podiformes de Calzadilla de los Barros(Macla, 2012) Merinero, Raul; Lunar Hernández, Rosario; Ortega Menor, Lorena; Piña GarcÃa, Rubén; Monterrubio, SerafÃn; Gervilla, FernandoItem Mineralogy of the Hydrothermal Alteration in the Námafjall Geothermal Field (Iceland)(Macla, 2011) Albert MÃnguez, Helena; Ortega Menor, Lorena; Lunar Hernández, Rosario; MartÃnez FrÃas, Jesús; Piña GarcÃa, Rubén